In the past, there have been known demand-response systems in which a power control apparatus controls the power usage of a plurality of devices owned by a plurality of power consumers, in accordance with requests to adjust power usage from a power supplier. For example, in the power control system disclosed in Japanese Laid-open Patent Application No. 2012-65407, a demand-response server controls the power usage of air conditioners and/or lighting devices installed in a plurality of buildings, in accordance with requests to adjust power usage of a power supplier.
To achieve accurate demand-response in a demand-response system such as that of Japanese Laid-open Patent Application No. 2012-65407, the demand-response server preferably controls power usage of devices using commands (control instructions) suitable for the control specifications of the devices. Especially, to achieve highly accurate demand-response, it is important to appropriately operate energy storage devices such as heat pump devices, and it is important to control the power usage of the energy storage devices using commands suitable for their control specifications.